I just had a serious bout with our sewer line (maybe fixed now) but the people who did the work also did an inspection of our plumbing. They measured our water pressure at 90psi and got really agitated about that being way too high and that I needed to install a PRV, immediately! A previous reading taken a year or so ago showed 80psi. I know it varies over time so I'm thinking of getting a gauge with the extra hand that records the max.

The house has all copper pipes installed around 1994 (probably not relevant).

The plumber gave a pretty big quote to install a PRV in the 1" line inside the garage just after the water line enters the garage. There is a gate valve on the line just outside the garage but it is from 1994 and *almost* turns the water off. Rather than trying to fix or replace it, I thought we would just install a PRV and shutoff inside the garage in the 1" copper pipe.

Now I'm seeing info on this forum that 90psi isn't really that bad. And if a PRV is installed, an expansion tank is also needed because the PRV has some kind of back flow prevention device in it. The plumber did not mention an expansion tank.

Have I got this kind of right? (My experience with plumbing is that if I touch it it will leak! That is, I'm totally inexperienced).